The present invention generally relates to apparatus for automating the treatment of muscular pain by intramuscular stimulation, and in particular, to improvement of the needles which are used with the apparatus to make the treatment process more comfortable for the patient.
Intramuscular stimulation (IMS) is a known method used to treat muscular pain by inserting a needle into an affected muscle. Intramuscular stimulation was first developed, and initially described by Gunn, "Dry Needling of Muscle Motor Points for Chronic Low-Back Pain: A Randomized Clinical Trial With Long-Term Follow-up", Spine, Vol. 5, No. 3, pp. 279-291 (1980). The intramuscular stimulation method has also been used by others (see, e.g., Chu, "Dry Needling in Myofascial Pain Related to Lumbosacral Radiculopathy", European Journal of Physical Medicine and Rehabilitation, Vol. 5, No. 4, pp. 106-121 (1995). A detailed method for performing the intramuscular stimulation treatment is described in Gunn, Treating Moyofascial Pain: Intramuscular Stimulation for Myofascial Pain Syndromes of Neuropathic Origin, Health Sciences Center for Educational Resources, University of Washington, Seattle Wash. (ISBN: 1-55910-003-6).
Briefly, the method involves the insertion of a fine needle, similar to an acupuncture needle, into the involved muscle and stimulating the muscle by repeatedly moving the needle back and forth linearly within the muscle. In this disclosure, "back and forth" movement will be taken to mean that the needle is first pushed in a linear direction into the muscle, then partially withdrawn in a linear direction, and then pushed back in, again along the same linear path of penetration. This action is repeated many times, at each of several muscular sites. For brevity, such needle manipulation will be referred to as "poking" in the remainder of this disclosure.
The involved muscle is usually tightly contracted. Such tightness of the muscle tends to apply severe pressure or pinching forces to the nerve fibers within the muscle, thereby causing chronic pain. When the contracted muscle is made to relax by repeated intramuscular stimulation treatments, the pain eventually subsides. The frequency of the treatment depends on the severity of the muscle contraction. A severely contracted muscle will require more frequent treatments over longer periods, whereas the required frequency will be less for the more lightly injured muscles. Intramuscular stimulation treatment is most usually performed at multiple points to be most effective.
Although the method developed by Gunn, and used by others, is quite effective in treating patients with chronic muscular pain, it was found that in practice, the method itself was self-limiting because of its detrimental effects on the person administering the treatment. To treat a patient, it is necessary to manually poke a needle into the injured muscle at a rate of approximately one to two times per second. Usually, a treatment session lasts about 45 minutes. This results in a total number of manual poking steps on the order of 2,700 to 5,400 times per session. For the case of a person treating eight patients per day, each with a 45 minute treatment session, the total number of manual poking steps will be on the order of 21,600 to 43,200 times per day. This enormous number of repeated, manual poking steps could at times cause such severe strain and pain to the shoulder and neck muscles of the person performing the treatment that, in time, damage to that person's muscles could itself require treatment (frequently, by an intramuscular stimulation treatment).
Another factor to consider is that the manual poking of the needle was itself very painful to the patient. This is presumably because the needle is constantly accelerated and decelerated during manual insertion and withdrawal during the course of a treatment. For this reason, the patient usually had to be premedicated (e.g., with narcotics) to avoid the excessive discomfort occurring during the treatment.
To overcome the problems associated with conventional intramuscular stimulation treatment, U.S. Pat. No. 5,735,868 discloses an automated, motor driven, needling instrument for administering an intramuscular stimulation treatment to patients suffering from chronic muscular pain. The disclosed apparatus replaces manually operated muscle stimulation with a muscle stimulator (a needle) which is mechanically linked to an electrically-driven motor, which is in turn electrically connected to a programmable control unit. In its preferred mode, the intramuscular needling device is mechanically linked to a linear action motor, allowing the motor to drive the needle continuously, back and forth within the muscle in a controlled manner. The person administering the treatment can then hold the instrument steadily at a desired treatment site while the motor provides controlled, uniform back and forth linear motion to the intramuscular stimulator needle, at fixed penetration depths. This was found to eliminate, to a great degree, the tedious muscle-straining labor involved in a conventional (manual) poking treatment, thereby relieving the physical burden on the person administering the treatment.
For extended intramuscular stimulation treatment sessions, a mechanical swivel arm is provided to hold the stimulator needling instrument, and a foot switch is provided to remotely turn the motor on and off. In this way, intramuscular stimulation treatments can be performed with minimal physical effort, helping to avoid muscle injury to the person administering the treatment.
A further, and major additional advantage resulting from the use of such a device is a dramatic reduction in the pain experienced by the patient during treatment. In a conventional, manual poking treatment, the needle is frequently accelerated and decelerated because of the uneven poking action which is inherent in a manual operation. This leads to a transient shearing action that is enormously painful to the patient. The constant speed and uniform motion provided by an automated poking apparatus has been found to eliminate such pain to a very significant degree (e.g., clinical tests have shown about a 75% reduction in the pain experienced by the patient during treatment).
In practice, the automated intramuscular stimulation apparatus disclosed in U.S. Pat. No. 5,735,868 has been found to work quite well in performing desired treatments. However, it has also been found that further improvements are possible for making the treatment process even more comfortable for the patient and more convenient for the person administering the treatment.
For example, the needle which is coupled with the apparatus to perform an intramuscular stimulation treatment is preferably of a very small diameter for efficient insertion into the skin and muscle tissue. In practice, an acupuncture needle has been found to work well for such purposes. However, unlike an acupuncture needle, which is inserted into the skin to a certain depth (generally only once) and which is then left in position for an appropriate amount of time before its extraction, the needle used with an intramuscular stimulation treatment apparatus must be repeatedly inserted into the skin and muscle tissue during a single treatment session.
It has been found that conventional, stainless-steel acupuncture needles are often not well suited for use with an intramuscular stimulation treatment apparatus because the surface of the needle tends to be relatively "sticky". As a result, the surrounding tissue tends to be pulled or pushed as the needle is reciprocated (in the direction of the needle), which has been found to cause pain to the patient during a treatment session. This can become particularly acute as the number of needle strokes needed for the treatment session increases.
For this reason, steps have been taken to minimize friction between the inserted needle and the surrounding tissue. One way in which this has been attempted is to use a needle which has been coated with a "non-stick" surface. For example, conventionally available, teflon-coated acupuncture needles have been used for such purposes. However, since the needle must be reciprocated in the skin and muscle tissue for a large number of strokes over an extended period of time during a single treatment session, the coating of a conventional teflon-coated acupuncture needle has been found to in many cases separate from the needle during the treatment session. This can itself cause pain to the patient, at the very least requiring replacement of the damaged needle.
It is therefore the principal object of the present invention to provide a needle for use with an intramuscular stimulation treatment apparatus which has a non-stick surface which is tightly adhered to the needle, so that the coating remains intact during the treatment session.
It is also an object of the present invention to provide a method for applying a non-stick coating to the surface of a needle for use with an intramuscular stimulation treatment apparatus, so that the coating remains intact during the treatment session.